Scroll machine with floating seal

ABSTRACT

A scroll machine utilizing working fluid under pressure to enhance axial sealing, including several embodiments of a multi-function floating seal to isolate the axial biasing fluid, and provide vacuum protection and a degree of high pressure ratio protection.

This is a continuation of U.S. patent application Ser. No. 591,454,filed Oct. 1, 1990, now abandoned.

The present invention relates to seals for scroll-type machinery, andmore particularly to a multi-function floating seal for axiallycompliant scroll compressors.

BACKGROUND AND SUMMARY OF THE INVENTION

A typical scroll machine has an orbiting scroll member having a spiralwrap on one face thereof, a non-orbiting scroll member having a spiralwrap on one face thereof, said wraps being intermeshed with one another,and means for causing said orbiting scroll member to orbit about an axiswith respect to said non-orbiting scroll member, whereby said wraps willcreate pockets of progressively changing volume.

To maximize efficiency, it is important for the wrap tips of each scrollmember to sealingly engage the end plate of the other scroll member sothat there is minimum leakage therebetween. One way this has beenaccomplished, other than by using tip seals (which are very difficult toassemble and which often present reliability problems) is by using fluidunder pressure to axially bias one of the scroll members against theother scroll member. This, of course, requires seals in order to isolatethe biasing fluid at the desired pressure. Accordingly, there is acontinuing need in the field of scroll machines for improved axialbiasing techniques including improved seals to facilitate same.

The seals of the present invention are embodied in a compressor andsuited for use in machines which use discharge pressure alone, dischargeand an independent intermediate pressure, or solely an intermediatepressure only, in order to provide the necessary axial biasing forces toenhance tip sealing. In addition, the seals of the present invention,which in most embodiments are three seals in one, are suitableparticularly for use in applications which bias the non-orbiting scroll.

It is therefore one of the primary objects of the present invention toprovide an improved seal which is relatively simple in construction,easy to install and inspect, and which effectively provides the complexsealing functions desired. The seals of the present invention providesignificant additional advantages. For example, the seal has beendiscovered to be particularly sensitive to the pressure ratio of thescroll machine and consequently provides particularly good protectionagainst vacuum conditions such as caused by reverse rotation or ablocked suction condition. In this condition, the seal will becomeineffective and thus permit discharge gas to be bypassed directly into azone of suction gas at suction gas pressure. This prevents the creationof a high vacuum on the inlet side of the compressor which mightotherwise occur and which could cause excessive and damaging forcespulling the scroll members together. Even more importantly, it preventsthe arcing or burning of the motor protector connector pins which hasbeen observed to occur under some vacuum conditions.

The seals of the present invention also, in some applications, provide adegree of temperature protection, particularly in motor-compressorswhere suction gas is used to cool the motor. This is because the sealwill leak from the high side to the low side at pressure differentialswhich are significantly higher than those for which the machine wasdesigned. This leakage of discharge fluid to the suction side of thecompressor will cause the machine to have a reduced output and theresulting heat build-up within the compressor enclosure due to thereduced flow of cooling gas will cause the standard motor protector totrip and shut the machine down. This characteristic of the seals of thepresent invention therefore provides a degree of protection in certainapplications from excessive discharge temperatures which could resultfrom loss of working fluid charge, or from a blocked condensor fan in arefrigeration system, or from an excessive discharge pressure (forwhatever reason). All of these undesirable conditions will cause ascroll machine to function at a pressure ratio greater than that whichis designed into the machine in terms of its predetermined fixed volumeratio.

These and other advantages of the present invention will become moreapparent when viewed in light of the accompanying drawings and followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a partial vertical sectional view through a scroll machine inwhich fluid pressure is used to bias the non-orbiting scroll memberaxially against the orbiting scroll member, and which embodies theprinciples of the present invention;

FIG. 2 is an enlarged vertical sectional view of a floating seal forminga part of the FIG. 1 fast embodiment of the invention, shown in itsrelaxed state;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2 and havingline 2--2 showing where the section of FIG. 2 is taken;

FIG. 4 is a view similar to FIG. 1 showing a second embodiment of thefloating seal of the present invention;

FIG. 5 is an enlarged vertical sectional view of a portion of the sealshown in FIG. 4;

FIG. 6 is an enlarged vertical sectional view of the floating seal ofthe embodiment of FIG. 4, shown in its relaxed state;

FIG. 7 is a sectional view taken along line 7--7 in FIG. 6 and havingline 6--6 showing where the section of FIG. 6 is taken;

FIG. 8 is a fragmentary view similar to FIG. 1 showing a thirdembodiment of the floating seal of the present invention;

FIG. 9 is an enlarged vertical cross-sectional view of the floating sealof FIG. 8, shown in its relaxed state; and

FIG. 10 is a sectional view taken along line 10--10 in FIG. 9

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is suitable for incorporation in manydifferent types of scroll machines, for exemplary purposes it will bedescribed herein incorporated in a scroll refrigerant compressor of thegeneral structure illustrated in vertical section in FIG. 1. Generallyspeaking, the compressor comprises a cylindrical hermetic shell 10having welded at the upper end thereof a cap 12, which is provided witha refrigerant discharge fitting 14 optionally having the usual dischargevalve therein (not shown). Other elements affixed to the shell include atransversely extending partition 16 which is welded about its peripheryat the same point that cap 12 is welded to shell 10, a main bearinghousing 18 which is affixed to shell 10 at a plurality of points in anydesirable manner, and a suction gas inlet fitting 17 having a gasdeflector 19 disposed in communication therewith inside the shell.

A motor stator 20 which is generally square in cross-section but withthe comers rounded off is press fit into shell 10. The flats between therounded comers on the stator provide passageways between the stator andshell, indicated at 22, which facilitate the flow of lubricant from thetop of the shell to the bottom. A crankshaft 24 having an eccentriccrank pin 26 at the upper end thereof is rotatably journaled in abearing 28 in main beating housing 18 and a second beating in a lowerbearing housing (not shown). Crankshaft 24 has at the lower end theusual relatively large diameter oil-pumping concentric bore (not shown)which communicates with a radially outwardly inclined smaller diameterbore 30 extending upwardly therefrom to the top of the crankshaft. Thelower portion of the interior shell 10 is filled with lubricating oil inthe usual manner and the pump at the bottom of the crankshaft is theprimary pump acting in conjunction with bore 30, which acts as asecondary pump, to pump lubricating fluid to all of the various portionsof the compressor which require lubrication.

Crankshaft 24 is rotatively driven by an electric motor including stator20, windings 32 passing therethrough, and a rotor 34 press fit on thecrankshaft and having one or more counterweights 36. A motor protector35, of the usual type, is provided in close proximity to motor windings32 so that if the motor exceeds its normal temperature range theprotector will deenergize the motor.

The upper surface of main bearing housing 18 is provided with an annularflat thrust bearing surface 38 on which is disposed an orbiting scrollmember 40 comprising an end plate 42 having the usual spiral vane orwrap 44 on the upper surface thereof, an annular flat thrust surface 46on the lower surface, and projecting downwardly therefrom a cylindricalhub 48 having a journal bearing 50 therein and in which is rotativelydisposed a drive bushing 52 having an inner bore 54 in which crank pin26 is drivingly disposed. Crank pin 26 has a flat on one surface (notshown) which drivingly engages a flat surface in a portion of bore 54(not shown) to provide a radially compliant driving arrangement, such asshown in assignee's U.S. Pat. No. 4,877,382, the disclosure of which isherein incorporated by reference.

Wrap 44 meshes with a non-orbiting spiral wrap 56 forming a part ofnon-orbiting scroll member 58 which is mounted to main bearing housing18 in any desired manner which will provide limited axial movement ofscroll member 58. The specific manner of such mounting is not criticalto the present invention, however, in the present embodiment, forexemplary purposes, non-orbiting scroll member 58 has a plurality ofcircumferentially spaced mounting bosses 60, one of which is shown, eachhaving a flat upper surface 62 and an axial bore 64 in which is slidablydisposed a sleeve 66 which is bolted to main bearing housing 18 by abolt 68 in the manner shown. Bolt 68 has an enlarged head having a flatlower surface 70 which engages surface 62 to limit the axially upper orseparating movement of non-orbiting scroll member, movement in theopposite direction being limited by axial engagement of the lower tipsurface of wrap 56 and the flat upper surface of orbiting scroll member40.

Non-orbiting scroll member 58 has a centrally disposed dischargepassageway 72 communicating with an upwardly open recess 74 which is influid communication via an opening 75 in partition 16 with the dischargemuffler chamber 76 defined by cap 12 and partition 16. Non-orbitingscroll member 58 has in the upper surface thereof an annular recess 78having parallel coaxial side walls in which is sealingly disposed forrelative axial movement an annular floating seal 80 which serves toisolate the bottom of recess 78 from the presence of gas under suctionand discharge pressure so that it can be placed in fluid communicationwith a source of intermediate fluid pressure by means of a passageway82. The non-orbiting scroll member is thus axially biased against theorbiting scroll member by the forces created by discharge pressureacting on the central portion of scroll member 58 and those created byintermediate fluid pressure acting on the bottom of recess 78. Thisaxial pressure biasing, as well as various techniques for supportingscroll member 58 for limited axial movement, are disclosed in muchgreater detail in assignee's aforesaid U.S. Pat. No. 4,877,382.

Relative rotation of the scroll members is prevented by the usual Oldhamcoupling comprising a ring 82 having a first pair of keys 84 (one ofwhich is shown) slidably disposed in diametrically opposed slots 86 (oneof which is shown) in scroll member 58 and a second pair of keys (notshown) slidably disposed in diametrically opposed slots (not shown) inscroll member 40.

The compressor is preferably of the "low side" type in which suction gasentering via deflector 19 is allowed, in part, to escape into the shelland assist in cooling the motor. So long as there is an adequate flow ofreturning suction gas the motor will remain within desired temperaturelimits. When this flow ceases, however, the loss of cooling will causemotor protector 35 to trip and shut the machine down.

The scroll compressor as thus far broadly described is either now knownin the art or is the subject matter of other pending applications forpatent by applicants' assignee. The details of construction whichincorporate the principles of the present invention are those which dealwith several embodiments of a novel multi-function floating seal.

With reference to FIGS. 1-5, the floating seal of the first embodimentis of a coaxial sandwiched construction and comprises an annular baseplate 100, east out of aluminum or the like, having a plurality ofequally spaced upstanding integral projections 102 each having anenlarged base portion 104. Disposed on plate 100 is an annular gasket106 formed of epoxy coated fiber gasket material having a plurality ofequally spaced holes which receive base portions 104, on top of which isdisposed a pair of normally flat identical lower lip seals 108 formed ofglass filled PTFE (approximately 5%) and optionally including 5% MoS₂ byweight. Seals 108 have a plurality of equally spaced holes which receivebase portions 104. On top of seals 108 is disposed an annular spacerplate 110, which can be a simple steel stamping, having annular recesses112 and 114 on the top and bottom surfaces thereof and a plurality ofequally spaced holes 119 which receive base portions 104, and on top ofplate 110 are a pair of normally flat identical annular upper lip seals116 formed of the same material as lip seals 108 and maintained incoaxial position by means of an annular upper seal plate 118 having aplurality of equally spaced holes receiving projections 102 and anannular rim 120 disposed in recess 112. Seal plate 118, which may beformed of grey east iron, has disposed about the inner periphery thereofan upwardly projecting planar sealing lip 122. The assembly is securedtogether by swaging the ends of each of the projections 101, asindicated at 123.

The overall seal assembly therefore provides three distinct seals;namely, an inside diameter seal at 124 and 126, an outside diameter sealat 128 and a top seal at 130, as best seen in FIG. 1. Seal 124 isbetween the inner periphery of lip seals 108 and the inside wall ofrecess 78, and seal 126 is between the inner periphery of lip seals 116and the inside wall of recess 78. Seals 124 and 126 isolate fluid underintermediate pressure in the bottom of recess 78 from fluid underdischarge pressure in recess 74. Seal 128 is between the outer peripheryof lip seals 108 and the outer wall of recess 78, and isolates fluidunder intermediate pressure in the bottom of recess 78 from fluid atsuction pressure within shell 10. Seal 130 is between lip seal 122 andan annular wear ring 132 formed of cast iron or the like and affixed topartition 16 by a suitable adhesive in a position surrounding opening75, and isolates fluid at suction pressure from fluid at dischargepressure across the top of the seal assembly. In lieu of a separate wearring 132 for the upper seal the lower surface of partition 16surrounding opening 75 can be locally hardened, by nitriding,carbonitriding or the like.

The diameter of seal 130 is chosen so that there is a positive upwardsealing force on seal 80 under normal operating conditions, i.e., atnormal pressure differentials. Therefore, when excessive pressuredifferentials are encountered, the seal will be forced downwardly bydischarge pressure, thereby permitting a leak of high side discharge gasdirectly across the seal to a zone of low side suction gas. If thisleakage is great enough then the resultant loss of flow of motor-coolingsuction gas (aggravated by the excessive temperature of the leakingdischarge gas) will cause the motor protector to trip, therebydeenergizing the motor. The width of seal 130 is chosen so that the unitpressure on the seal itself (i.e., between seal 122 and seat 132) isgreater than normally encountered discharge pressure, thus insuringconsistant sealing.

With reference to FIGS. 4-7, the floating seal of the second embodimentis also of a coaxial sandwiched construction and comprises an annularbase plate 200, cast out of aluminum or the like and having an annularupstanding integral rib 202. Disposed on plate 200 is a lower inner lipseal 204 formed of 5% glass and 5% molydisulfide filled PTFE and havinga conical resilient sealing lip 206; and an outer lip seal 208 of thesame material having a resilient conical sealing lip 210. Disposed ontop of inner seal 204 and inside rib 202 is an annular metal separatorplate 212 having minutely ribbed upper and lower surfaces 212a and 212bto increase mechanical contact with the seals. On top of plate 212 are apair of identical annular upper lip seals 214 formed of the samematerial as lip seals 204 and 208, also maintained in coaxial positionby means of an annular rib 202, and an upper seal plate 216 havingdisposed about the inner periphery thereof an upwardly projecting planarsealing lip 218. Seals 214 have resilient conical inner sealing lips220. Seal plate 216 is preferably formed of cast iron. Outer seal 208 isretained in place by an annular metal ring 222, and the entire assemblyis secured together by swaging the top of rib 202 at spaced locations,as indicated at 224.

This seal assembly also provides three distinct seals; namely, an insidediameter seal at 226 and 228, an outside diameter seal at 230 and a topseal at 232, as best seen in FIG. 4. Seal 226 is between the innerperiphery of lip seal 204 and the inside wall of recess 78, and seal 228is between the inner periphery of lip seals 214 and the inside wall ofrecess 78. Seals 226 and 228 isolate fluid under intermediate pressurein the bottom of recess 78 from fluid under discharge pressure in recess74. Seal 230 is between the outer periphery of lip seal 208 and theouter wall of recess 78, and isolates fluid under intermediate pressurein the bottom of recess 78 from fluid at suction pressure within shell10. Seal 232 is between lip seal 218 and annular wear ring 132surrounding opening 75 in partition 16, and isolates fluid at suctionpressure from fluid at discharge pressure across the top of the sealassembly. The diameter and width of the top seal are chosen in the samemanner as for the fast embodiment.

With reference to FIG. 8-10, the floating seal of the third embodimentis also of a coaxial sandwiched construction and comprises an annularbase plate 300, cast out of aluminum or the like, having a plurality ofequally spaced upstanding integral projections 302 projecting from ashallow annular rib 304. Disposed on the inner periphery of plate 300inside rib 304 are a pair of normally flat identical inner lip seals 306formed of suitably filled PTFE. Disposed on top of the outer peripheryof plate 300, outside rib 304, are a pair of normally flat identicalannular outer lip seals 308 formed of the same material as lip seals306. Both pairs of seals are maintained in coaxial position by means ofrib 304, and are clamped in place by an annular upper seal plate 310having a plurality of equally spaced holes receiving projections 302.Seal plate 310, which is preferably formed of grey cast iron, stampedsteel or powdered metal, has disposed about the inner periphery thereofan upwardly projecting planar sealing lip 312. The assembly is securedtogether by swaging the ends of each of the projections 302, asindicated at 314.

Again, the overall seal assembly therefor provides three distinct seals;namely, an inside diameter seal at 316, an outside diameter seal at 318and a top seal at 320, as best seen in FIG. 8. Seal 316 is between theinner periphery of lip seals 306 and the inside wall of recess 78. Seal316 isolates fluid under intermediate pressure in the bottom of recess78 from fluid under discharge pressure in recess 74. Seal 318 is betweenthe outer periphery of lip seals 308 and the outer wall of recess 78,and isolates fluid under intermediate pressure in the bottom of recess78 from fluid at suction pressure within shell 10. Seal 320 is betweenlip seal 312 and annular wear ring 132 surrounding opening 75 inpartition 16, and isolates fluid at suction pressure from fluid atdischarge pressure across the top of the seal assembly. The diameter andwidth of the top seal are chosen in the same manner as for the firstembodiment.

In order to prevent excessive intermediate pressure from building upbetween the inner and outer seals, which would occur in a liquidslugging situation and could blow out the high side seal, a suitablevent can be provided, such as at 123 in FIG. 2 and at 316 in FIG. 8.

While this invention has been described in connection with theseparticular examples, no limitation is intended except as defined by thefollowing claims. The skilled practitioner will realize that othermodifications may be made without departing from the spirit of thisinvention after studying the specification and drawings.

We claim:
 1. A scroll machine comprising:(a) a hermetic shell; (b) anorbiting scroll member disposed in said shell and having a first spiralwrap on one face thereof; (c) a non-orbiting scroll member disposed insaid shell and having a second spiral wrap on one face thereof, saidwraps being intermeshed with one another; (d) means for causing saidorbiting scroll member to orbit about an axis with respect to saidnon-orbiting scroll member whereby said wraps will create pockets ofprogressively changing volume between a suction pressure zone and adischarge pressure zone; (e) means for mounting one of said scrollmembers for limited axial movement with respect to the other scrollmember; (f) means defining an annular cavity exposed to a surface of oneof said scroll members which will cause pressurized fluid in said cavityto bias said one scroll member toward the other scroll member, saidcavity having a radially inner wall surface and a radially outer wallsurface; (g) means defining a fluid leakage path between said cavity andthe interior of said shell; (h) means for supplying fluid under pressureto said cavity for biasing said scroll members axially together; and (i)annular seal means disposed in said cavity, said seal means having firstand second seals sealingly engaging said inner and outer wall surfaces,respectively, to isolate said pressurized fluid in said cavity from saidleakage path and said discharge pressure zone.
 2. A scroll machine asclaimed in claim 1 wherein said inner and outer wall surfaces arecylindrical and coaxial.
 3. A scroll machine as claimed in claim 1wherein said machine is a compressor and said pressurized fluid is theworking fluid being compressed from a suction pressure to a dischargepressure.
 4. A scroll machine as claimed in claim 3 wherein saidpressurized fluid is at a pressure intermediate said suction pressureand discharge pressure.
 5. A scroll machine as claimed in claim 1wherein said seal means floats axially in said cavity.
 6. A scrollmachine as claimed in claim 1 wherein said seal means is of sandwichconstruction comprising a first annular element and a second annularelement, and wherein said first and second seals comprise generally flatinner and outer annular lip seals clamped between said elements.
 7. Ascroll machine as claimed in claim 6 wherein said inner and outer lipseals are integral with one another.
 8. A scroll machine as claimed inclaim 6 wherein said inner and outer lip seals are separate parts.
 9. Ascroll machine as claimed in claim 6 wherein said lip seals are formedof a filled PTFE material.
 10. A scroll machine as claimed in claim 9wherein said PTFE is filled with glass.
 11. A scroll machine as claimedin claim 10 wherein said glass is approximately 5% by weight of the sealmaterial.
 12. A scroll machine as claimed in claim 9 wherein said PTFEis filled with MoS₂.
 13. A scroll machine as claimed in claim 12 whereinsaid MoS₂ is approximately 5% by weight of the seal material.
 14. Ascroll machine as claimed in claim 6 wherein said lip seals are planarin configuration when in an unstressed state.
 15. A scroll machine asclaimed in claim 6 wherein said lip seals each having a slightly conicalexposed periphery when in an unstressed state.
 16. A scroll machine asclaimed in claim 15 wherein there are a plurality of inner and outer lipseals.
 17. A scroll machine as claimed in claim 6 wherein there are aplurality of inner lip seals having an annular spacer element disposedtherebetween.
 18. A scroll machine as claimed in claim 17 wherein saidspacer element is formed of a relatively rigid material having aplurality of ridges on the portions of its surface which engage said lipseals.
 19. A scroll machine as claimed in claim 6 wherein said firstelement has a plurality of circumferentially spaced axially extendingposts extending through said second element.
 20. A scroll machine asclaimed in claim 19 wherein the free ends of said posts are swedged toclamp said lip seals between said elements.
 21. A scroll machine asclaimed in claim 19 wherein said lip seals are integral with one anotherand said post extends therethrough.
 22. A scroll machine as claimed inclaim 19 wherein said inner and outer lip seals are separate parts andsaid posts extend therebetween.
 23. A scroll machine as claimed in claim6 wherein there are a plurality of inner lip seals.
 24. A scroll machineas claimed in claim 6 wherein said seal means floats axially in saidcavity.
 25. A scroll machine as claimed in claim 1 wherein said onescroll member is said non-orbiting scroll member.
 26. A scrollcompressor comprising:(a) a hermetic shell; (b) an orbiting scrollmember disposed in said shell and having a first spiral wrap on one facethereof; (c) a non-orbiting scroll member disposed in said shell andhaving a second spiral wrap on one face thereof, said wraps beingintermeshed with one another; (d) means for causing said orbiting scrollmember to orbit about an axis with respect to said non-orbiting scrollmember whereby said wraps will create pockets of progressivelydecreasing volume to compress a fluid from a suction pressure to adischarge pressure; (e) means for mounting one of said scroll membersfor limited axial movement with respect to the other scroll member; (f)means defining a cavity exposed to a surface of one of said scrollmembers which will cause pressurized fluid in said cavity to bias saidone scroll member toward the other scroll member; (g) means defining afirst fluid leakage path between said cavity and a zone in said shell atsuction pressure; (h) means defining a second fluid leakage path betweensaid cavity and a zone in said shell at discharge pressure; (i) meansfor supplying fluid to said cavity at a pressure intermediate saidsuction and discharge pressures for biasing said scroll members axiallytogether; and (j) seal means disposed in said cavity, said seal meanshaving . .three seals, said.!. .Iadd.a .Iaddend.first seal isolatingsaid pressurized fluid in said cavity from said first leakage path, ..said.!. .Iadd.a .Iaddend.second seal isolating said cavity from saidsecond leakage path, and . .said.!. .Iadd.a .Iaddend.third seal ..isolating.!. .Iadd.engaging a different component of said compressor toisolate .Iaddend.fluid at suction pressure from fluid at dischargepressure across a face of said seal means.
 27. A scroll machine asclaimed in claim 26 wherein said seal means floats axially in saidcavity with said first and second seals remaining effective.
 28. AscroIl machine as claimed in claim 26 wherein said seal means is ofsandwich construction comprising a first annular element and a secondannular element, and wherein said first and second seals comprisegenerally flat inner and outer annular lip seals clamped between saidelements.
 29. A scroll machine as claimed in claim 28 wherein said innerand outer lip seals are integral with one another.
 30. A scroll machineas claimed in claim 28 wherein said inner and outer lip seals areseparate parts.
 31. A scroll machine as claimed in claim 28 whereinthere are a plurality of inner lip seals having an annular spacerelement disposed therebetween.
 32. A scroll machine as claimed in claim26 wherein all of said seals are annular in configuration, said thirdseal being of a diameter which provides a positive net scaling forceunder normal operating conditions.
 33. A scroll machine as claimed inclaim 32 wherein said third seal is of a width such that the unitpressure thereon in a sealing direction is greater than normal dischargepressure.
 34. A scroll machine as claimed in claim 26 wherein said sealmeans floats axially in said cavity and wherein the existence of avacuum at the suction inlet of said compressor will cause said sealmeans to move axially and render said third seal ineffective.
 35. Amulti-function seal assembly comprising:(a) an annular inner lip sealadapted to sealingly engage the outside of a first cylindrical surface;(b) an annular outer lip seal adapted to sealingly engage the inside ofa second cylindrical surface, said seal assembly being mounted formovement along the center axes of said seals; (c) first and secondclamping elements clamping said inner and outer seals therebetween; and(d) a third annular seal operatively associated with one of saidelements and being adapted to sealingly engage a generally flat annularsealing surface.
 36. A multi-function seal assembly as claimed in claim35 wherein said three seals are coaxial with one another.
 37. Amulti-function seal assembly as claimed in claim 35 wherein said firstand second cylindrical surfaces define the side walls of an annularcavity, said sealing surface being disposed opposite the bottom of saidcavity.
 38. A scroll machine comprising:(a) a hermetic shell; (b) anorbiting scroll member disposed in said shell and having a first spiralwrap on one face thereof; (c) a non-orbiting scroll member in said shelland having a second spiral wrap on one face thereof, said wraps beingintermeshed with one another; (d) means for causing said orbiting scrollmember to orbit about an axis with respect to said non-orbiting scrollmember whereby said wraps will create pockets of progressively changingvolume; (e) means for mounting one of said scroll members for limitedaxial movement with respect to the other scroll member; (f) meansdefining an annular cavity exposed to a surface on one of said scrollmembers which will cause pressurized fluid in said cavity to bias saidone scroll member toward the other scroll member, said cavity having aradial inner wall surface and a radial outer wall surface; (g) meansdefining a fluid leakage path between said cavity and the interior ofsaid shell; (h) means for supplying fluid under pressure to said cavityfor biasing said scroll members axially together; and (i) annular sealmeans disposed in said cavity, said seal means having first and secondseals sealingly engaging said inner and outer wall surfaces,respectively, to isolate said pressurized fluid in said cavity from saidleakage path, said seal means being of sandwich construction comprisinga first annular element having an annular axially extending rib and asecond annular element formed of two annular parts disposed on oppositesides of said rib wherein said first and second seals comprise generallyflat inner and outer annular lip seals clamped between said elements.39. A scroll machine comprising:(a) a hermetic shell; (b) an orbitingscroll member disposed in said shell and having a first spiral wrap onone face thereof; (c) a non-orbiting scroll member in said shell andhaving a second spiral wrap on one face thereof, said wraps beingintermeshed with one another; (d) means for causing said orbiting scrollmember to orbit about an axis with respect to said non-orbiting scrollmember whereby said wraps will create pockets of progressively changingvolume; (e) means for mounting one of said scroll members for limitedaxial movement with respect to the other scroll member; (f) meansdefining an annular cavity exposed to a surface of one of said scrollmembers which will cause pressurized fluid in said cavity to bias saidone scroll member toward the other scroll member, said cavity having aradially inner wall surface and a radially outer wall surface; (g) meansdefining a fluid leakage path between said cavity and the interior ofsaid shell; (h) means for supplying fluid under pressure to said cavityfor biasing said scroll members axially together; and (i) annular sealmeans disposed in said cavity, said seal means having first and secondseals sealingly engaging said inner and outer wall surfaces,respectively, to isolate said pressurized fluid in said cavity from saidleakage path, said seal means being of sandwich construction comprisinga first annular element having an annular axially extending rib and asecond annular element formed of two annular parts disposed on oppositesides of said rib wherein said first and second seals comprise generallyflat inner and outer annular lip seals clamped between said elements andwherein said rib is swedged at circumferentially spaced points to clampsaid two annular parts and said lip seals between said elements.
 40. Ascroll compressor comprising:(a) a hermetic shell; (b) an orbitingscroll member disposed in said shell and having a first spiral wrap onone face thereof; (c) a non-orbiting scroll member in said shell andhaving a second . .signal.!. .Iadd.spiral .Iaddend.wrap on one facethereof, said wraps being intermeshed with one another; (d) means forcausing said orbiting scroll member to orbit about an axis with respectto said non-orbiting scroll member whereby said wraps will createpockets of progressively changing volume; (e) means for mounting one ofsaid scroll members for limited axial movement with respect to the otherscroll member; (f) means defining an annular cavity exposed to a surfaceof one of said scroll members which will cause pressurized fluid in saidcavity to bias said one scroll member toward the other scroll member,said cavity having a radially inner wall surface and a radially outerwall surface; (g) means defining a first fluid leakage path between saidcavity and the interior of said shell; (h) means defining a second fluidleakage path between said cavity and a zone in said shell at dischargepressure; (i) means for supplying fluid under pressure to said cavityfor biasing said scroll members axially together; and (j) annular sealmeans disposed in said cavity, said seal means having first and secondseals sealingly engaging said inner and outer wall surfaces,respectively, to isolate said pressurized fluid in said cavity from said.Iadd.first and second .Iaddend.leakage . .path.!. .Iadd.paths.Iaddend.,said seal means being of sandwich construction comprising a firstannular element having an annular axially extending rib and a secondannular element formed of two annular parts disposed on opposite sidesof said rib wherein said first and second seals comprise generally flatinner and outer annular lip seals clamped between said elements; whereinone face of said seal means is exposed to the fluid in said cavity withsaid first seal isolating said cavity from said discharge pressure zoneand said second seal isolating said cavity from the interior of saidshell, the opposite face of said seal means being exposed to both theinterior of said shell and to discharge pressure, said seal means ..comprising.!. .Iadd.engaging another component of said compressor todefine .Iaddend.a third annular seal for isolating the interior of saidshell from discharge pressure across said opposite face of said sealmeans.
 41. A scroll compressor comprising:(a) a hermetic shell; (b) anorbiting scroll member disposed in said shell and having a first spiralwrap on one face thereof; (c) a non-orbiting scroll member in said shelland having a second spiral wrap on one face thereof, said wraps beingintermeshed with one another; (d) means for causing said orbiting scrollmember to orbit about an axis with respect to said non-orbiting scrollmember whereby said wraps will create pockets of progressively changingvolume; (e) means for mounting one of said scroll members for limitedaxial movement with respect to the other scroll member; (f) meansdefining an annular cavity exposed to a surface of one of said scrollmembers which will cause pressurized fluid in said cavity to bias saidone scroll member toward the other scroll member, said cavity having aradially inner wall surface and a radially outer wall surface; (g) meansdefining a first fluid leakage path between said cavity and the interiorof said shell; (h) means defining a second fluid leakage path betweensaid cavity and a zone in said shell at discharge pressure; (i) meansfor supplying fluid under pressure to said cavity for biasing saidscroll members axially together; and (j) annular seal means disposed insaid cavity, said seal means having first and second seals sealinglyengaging said inner and outer wall surfaces, respectively, to isolatesaid pressurized fluid in said cavity from said .Iadd.first and second.Iaddend.leakage paths, said seal means being of sandwich constructioncomprising a first annular element having an annular axially extendingrib and a second annular element formed of two annular parts disposed onopposite sides of said rib wherein said first and second seals comprisegenerally flat inner and outer annular lip seals clamped between saidelements; wherein one face of said seal means is exposed to the fluid insaid cavity with said first seal isolating said cavity from saiddischarge pressure zone and said second seal isolating said cavity fromthe interior of said shell, the opposite face of said seal means beingexposed to both the interior of said shell and to discharge pressure,said seal means . .comprising.!. .Iadd.engaging another component ofsaid compressor to define .Iaddend.a third annular seal for isolatingthe interior of said shell from discharge pressure across said oppositeface of said seal means and wherein said third seal is integral withsaid second element of said seal means.
 42. A scroll compressorcomprising:(a) a hermetic shell; (b) a discharge fluid port in apartition disposed in said shell; (c) an orbiting scroll member disposedin said shell and having a first spiral wrap on one face thereof; (d) anon-orbiting scroll member in said shell and having a second spiral wrapon one face thereof, said wraps being intermeshed with one another; (e)means for causing said orbiting scroll member to orbit about an axiswith respect to said non-orbiting scroll member whereby said wraps willcreate pockets of progressively changing volume; (f) means for mountingone of said scroll members for limited axial movement with respect tothe other scroll member; (g) means defining an annular cavity exposed toa surface of one of said scroll members which will cause pressurizedfluid in said cavity to bias said one scroll member toward the otherscroll member, said cavity having a radially inner wall surface and aradially outer wall surface; (h) means defining a first fluid leakagepath between said cavity and the interior of said shell; (i) meansdefining a second fluid leakage path between said cavity and a zone insaid shell at discharge pressure; (j) means for supplying fluid underpressure to said cavity for biasing said scroll members axiallytogether; and (k) annular seal means disposed in said cavity, said sealmeans having first and second seals sealingly engaging said inner andouter wall surfaces, respectively, to isolate said pressurized fluid insaid cavity from said .Iadd.first and second .Iaddend.leakage . .path.!..Iadd.paths.Iaddend., said seal means being of a sandwich constructioncomprising a first annular element and a second annular element whereinsaid first and second seals comprise generally flat inner and outerannular lip seals clamped between said elements; wherein one face ofsaid seal means is exposed to the fluid in said cavity with said firstseal isolating said cavity from said discharge pressure zone and saidsecond seal isolating said cavity from the interior of said shell, theopposite face of said seal means being exposed to both the interior ofsaid shell and to discharge pressure, said seal means . .comprising.!..Iadd.engaging another component of said compressor to define .Iaddend.athird annular seal for isolating the interior of said shell fromdischarge pressure across said opposite face of said seal means saidthird seal surrounding said discharge fluid port.
 43. A scrollcompressor comprising:(a) a hermetic shell; (b) a discharge fluid portin a partition disposed in said shell; (c) a hardened valve seat on saidpartition surrounding said discharge fluid port; (d) an orbiting scrollmember disposed in said shell and having a first spiral wrap on one facethereof; (e) a non-orbiting scroll member in said shell and having asecond spiral wrap on one face thereof, said wraps being intermeshedwith one another; (f) means for causing said orbiting scroll member toorbit about an axis with respect to said non-orbiting scroll memberwhereby said wraps will create pockets of progressively changing volume;(g) means for mounting one of said scroll members for limited axialmovement with respect to the other scroll member; (h) means defining anannular cavity exposed to a surface of one of said scroll members whichwill cause pressurized fluid in said cavity to bias said one scrollmember toward the other scroll member, said cavity having a radiallyinner wall surface and a radially outer wall surface; (i) means defininga first fluid leakage path between said cavity and the interior of saidshell; (g) means defining a second fluid leakage path between saidcavity and a zone in said shell at discharge pressure; (k) means forsupplying fluid under pressure to said cavity for biasing said scrollmembers axially together; and (l) annular seal means disposed in saidcavity, said seal means having first and second seals sealingly engagingsaid inner and outer wall surfaces, respectively, to isolate saidpressurized fluid in said cavity from said .Iadd.first and second.Iaddend.leakage . .path.!. .Iadd.paths.Iaddend., said seal means beingof a sandwich construction comprising a first annular element and asecond annular element wherein said first and second seals comprisegenerally flat inner and outer annular lip seals clamped between saidelements; wherein one face of said seal means is exposed to the fluid insaid cavity with said first seal isolating said cavity from saiddischarge pressure zone and said second seal isolating said cavity fromthe interior of said shell, the opposite face of said seal means beingexposed to both the interior of said shell and to discharge pressure,said seal means . .comprising.!. .Iadd.engaging another component ofsaid compressor to define .Iaddend.a third annular seal for isolatingthe interior of said shell from discharge pressure across said oppositeface of said seal means said third seal surrounding said discharge fluidport.
 44. A scroll compressor comprising:(a) a hermetic shell; (b) adischarge fluid port in a partition disposed in said shell; (c) ahardened valve seat on said partition surrounding said discharge fluidport, said valve seat being a separate annular member affixed to saidpartitions and surrounding said discharge fluid port; (d) an orbitingscroll member disposed in said shell and having a first spiral wrap onone face thereof; (e) a non-orbiting scroll member in said shell andhaving a second spiral wrap on one face thereof, said wraps beingintermeshed with one another; (f) means for causing said orbiting scrollmember to orbit about an axis with respect to said non-orbiting scrollmember whereby said wraps will create pockets of progressively changingvolume; (g) means for mounting one of said scroll members for limitedaxial movement with respect to the other scroll member; (h) meansdefining an annular cavity exposed to a surface of one of said scrollmembers which will cause pressurized fluid in said cavity to bias saidone scroll member toward the other scroll member, said cavity having aradially inner wall surface and a radially outer wall surface; (i) meansdefining a first fluid leakage path between said cavity and the interiorof said shell; (j) means defining a second fluid leakage path betweensaid cavity and a zone in said shell at discharge pressure; (k) meansfor supplying fluid under pressure to said cavity for biasing saidscroll members axially together; and (l) annular seal means disposed insaid cavity, said seal means having first and second seals sealinglyengaging said inner and outer wall surfaces, respectively, to isolatesaid pressurized fluid in said cavity from said .Iadd.first and second.Iaddend.leakage . .path.!. .Iadd.paths.Iaddend., said seal means beingof a sandwich construction comprising a first annular element and asecond annular element wherein said first and second seals comprisegenerally flat inner and outer annular lip seals clamped between saidelements; wherein one face of said seal means is exposed to the fluid insaid cavity with said first seal isolating said cavity from saiddischarge pressure zone and said second seal isolating said cavity fromthe interior of said shell, the opposite face of said seal means beingexposed to both the interior of said shell and to discharge pressure,said seal means . .comprising.!. .Iadd.engaging another component ofsaid compressor to define .Iaddend.a third annular seal for isolatingthe interior of said shell from discharge pressure across said oppositeface of said seal means said third seal surrounding said discharge fluidport.
 45. A scroll compressor comprising:(a) a hermetic shell; (b) adischarge fluid port in a partition disposed in said shell; (c) ahardened valve seat on said partition surrounding said discharge fluidport, said valve seat being a locally hardened surface on said partitionsurrounding said discharge fluid port; (d) an orbiting scroll memberdisposed in said shell and having a first spiral wrap on one facethereof; (e) a non-orbiting scroll member in said shell and having asecond spiral wrap on one face thereof, said wraps being intermeshedwith one another; (f) means for causing said orbiting scroll member toorbit about an axis with respect to said non-orbiting scroll memberwhereby said wraps will create pockets of progressively changing volume;(g) means for mounting one of said scroll members for limited axialmovement with respect to the other scroll member; (h) means defining anannular cavity exposed to a surface of one of said scroll members whichwill cause pressurized fluid in said cavity to bias said one scrollmember toward the other scroll member, said cavity having a radiallyinner wall surface and a radially outer wall surface; (i) means defininga first fluid leakage path between said cavity and the interior of saidshell; (j) means defining a second fluid leakage path between saidcavity and a zone in said shell at discharge pressure; (k) means forsupplying fluid under pressure to said cavity for biasing said scrollmembers axially together; and (l) annular seal means disposed in saidcavity, said seal means having first and second seals sealingly engagingsaid inner and outer wall surfaces, respectively, to isolate saidpressurized fluid in said cavity from said .Iadd.first and second.Iaddend.leakage . .path.!. .Iadd.paths.Iaddend., said seal means beingof sandwich construction comprising a first annular element having anannular axially extending rib and a second annular element formed of twoannular parts disposed on opposite sides of said rib wherein said firstand second seals comprise generally flat inner and outer annular lipseals clamped between said elements; wherein one face of said seal meansis exposed to the fluid in said cavity with said first seal isolatingsaid cavity from said discharge pressure zone and said second sealisolating said cavity from the interior of said shell, the opposite faceof said seal means being exposed to both the interior of said shell andto discharge pressure, said seal means . .comprising.!. .Iadd.engaginganother component of said compressor to define .Iaddend.a third annularseal for isolating the interior of said shell from discharge pressureacross said opposite face of said seal means said third seal surroundingsaid discharge fluid port.
 46. A scroll compressor having a dischargezone at discharge pressure comprising:(a) a hermetic shell; (b) anorbiting scroll member disposed in said shell and having a first spiralwrap on one face thereof; (c) a non-orbiting scroll member in said shelland having a second spiral wrap on one face thereof, said wraps beingintermeshed with one another; (d) means for causing said orbiting scrollmember to orbit about an axis with respect to said non-orbiting scrollmember whereby said wraps will create pockets of progressively changingvolume; (e) means for mounting one of said scroll members for limitedaxial movement with respect to the other scroll member; (f) meansdefining an annular cavity exposed to a surface of one of said scrollmembers which will cause pressurized fluid in said cavity to bias saidone scroll member toward the other scroll member, said cavity having aradially inner wall surface and a radially outer wall surface; (g) meansdefining a first fluid leakage path between said cavity and the interiorof said shell; (h) means defining a second fluid leakage path betweensaid cavity and a zone in said shell at discharge pressure; (i) meansfor supplying fluid under pressure to said cavity for biasing saidscroll members axially together; and (j) annular seal means disposed insaid cavity, said seal means having first and second seals sealinglyengaging said inner and outer wall surfaces, respectively, to isolatesaid pressurized fluid in said cavity from said .Iadd.first and second.Iaddend.leakage . .path.!. .Iadd.paths.Iaddend.; wherein one face ofsaid seal means is exposed to the fluid in said cavity with said firstseal isolating said cavity from said discharge pressure zone and saidsecond seal isolating said cavity from the interior of said shell, theopposite face of said seal means being exposed to both the interior ofsaid shell and to discharge pressure, said seal means . .comprising.!..Iadd.engaging another component of said compressor to define .Iaddend.athird annular seal for isolating the interior of said shell fromdischarge pressure across said opposite face of said seal means saidthird seal surrounding said discharge fluid port.
 47. A scrollcompressor having a discharge zone at discharge pressure machinecomprising:(a) a hermetic shell; (b) an orbiting scroll member disposedin said shell and having a first spiral wrap on one face thereof; (c) anon-orbiting scroll member disposed in said shell and having a secondspiral wrap on one face thereof, said wraps being intermeshed with oneanother; (d) means for causing said orbiting scroll member to orbitabout an axis with respect to said non-orbiting scroll member wherebysaid wraps will create pockets of progressively changing volume; (e)means for mounting one of said scroll members for limited axial movementwith respect to the other scroll member; (f) means defining an annularcavity exposed to a surface on one of said scroll members which willcause pressurized fluid in said cavity to bias said one scroll membertoward the other scroll member, said cavity having a radial inner wallsurface and a radial outer wall surface; (g) means defining a firstfluid leakage path between said cavity and the interior of said shell;(h) means defining a second fluid leakage path between said cavity andsaid discharge zone; (i) means for supplying fluid under pressure tosaid cavity for biasing said scroll members axially together; and (j)annular seal means disposed in said cavity, said seal means having firstand second seals sealingly engaging said inner and outer wall surfaces,respectively, to isolate said pressurized fluid in said cavity from said.Iadd.first and second .Iaddend.leakage . .path.!. .Iadd.paths.Iaddend.;wherein one face of said seal means is exposed to the fluid in saidcavity with said first seal isolating said cavity from said dischargepressure zone and said second seal isolating said cavity from theinterior of said shell, the opposite face of said seal means beingexposed to both the interior of said shell and to discharge pressure,said seal means . .comprising.!. .Iadd.engaging another component ofsaid compressor to define .Iaddend.a third annular seal for isolatingthe interior of said shell from discharge pressure across said oppositeface of said seal means, said third seal being integral with said secondelement of said seal means. .Iadd.
 48. A scroll machine comprising:(a) ahermetic shell; (b) an orbiting scroll member disposed in said shell andhaving a first spiral wrap on one face thereof; (c) a non-orbitingscroll member disposed in said shell and having a second spiral wrap onone face thereof, said spiral wraps being intermeshed with one another;(d) means for causing said orbiting scroll member to orbit about an axiswith respect to said non-orbiting scroll member whereby said wraps willcreate pockets of progressively changing volume between a suctionpressure zone defining a suction pressure and a discharge pressure zonedefining a discharge pressure; (e) means defining a cavity disposedwithin one of said scroll members; (f) means defining a fluid pathbetween said discharge pressure zone and said suction pressure zone; (g)means for supplying intermediate pressurized fluid to said cavity, saidintermediate pressurized fluid being at a pressure inbetween saidsuction and discharge pressures; and (h) seal means disposed in saidcavity to isolate said intermediate pressurized fluid in said cavitywhereby said seal means engages another component of said compressor toclose said fluid path and said discharge pressure zone..Iaddend..Iadd.49. A scroll machine as claimed in claim 48 wherein saidone scroll member is said non-orbiting scroll member. .Iaddend..Iadd.50.A scroll machine as claimed in claim 48 wherein said seal means floatsaxially in said cavity between a first position wherein said seal meansisolates fluid in said suction pressure zone from fluid in saiddischarge pressure zone and a second position wherein fluid in saiddischarge pressure zone is leaked to said suction pressure zone..Iaddend..Iadd.51. A scroll machine as claimed in claim 50 wherein saidseal means is disposed in said first position under normal operatingconditions. .Iaddend..Iadd.52. A scroll machine as claimed in claim 50wherein said seal means moves to said second position when the ratiobetween said discharge pressure and said suction pressure exceeds apredefined limit. .Iaddend..Iadd.53. A scroll machine as claimed inclaim 48 wherein said intermediate pressurized fluid reacts against asurface of said one scroll member to bias said one scroll member towardthe other scroll member. .Iaddend..Iadd.54. A scroll machine as claimedin claim 48 wherein said cavity is substantially defined by saidnon-orbiting scroll member. .Iaddend..Iadd.55. A scroll machine asclaimed in claim 48 including a leakage path between said cavity andsaid suction pressure zone. .Iaddend..Iadd.56. A scroll machine asclaimed in claim 48 wherein said seal means provides a first sealisolating said cavity from said discharge pressure zone, and a secondseal isolating said cavity from said suction pressure zone, saidengagement creating a third seal isolating said discharge pressure zonefrom said suction pressure zone. .Iaddend..Iadd.57. A scroll machinecomprising:(a) a hermetic shell; (b) an orbiting scroll member disposedin said shell and having a first spiral wrap on one face thereof; (c) anon-orbiting scroll member disposed in said shell and having a secondspiral wrap on one face thereof, said spiral wraps being intermeshedwith one another; (d) means for causing said orbiting scroll member toorbit about an axis with respect to said non-orbiting scroll memberwhereby said wraps will create pockets of progressively changing volumeto compress a working fluid between a suction pressure zone defining asuction pressure and a discharge pressure zone defining a dischargepressure; (e) means defining a cavity disposed within one of said scrollmembers; (f) means defining a fluid path between said discharge pressurezone and said suction pressure zone; (g) means for supplying saidworking fluid under pressure to said cavity; and (h) seal means disposedto move in said cavity between a first position wherein said seal meansengages another component of said scroll machine to isolate saiddischarge pressure zone from said suction pressure zone and a secondposition in which a leakage of fluid in said discharge pressure zoneinto said suction pressure zone is permitted. .Iaddend..Iadd.58. Ascroll machine as claimed in claim 57 wherein said working fluid beingsupplied to said cavity is at a pressure intermediate said suctionpressure and said discharge pressure. .Iaddend..Iadd.59. A scrollmachine as claimed in claim 57 wherein said seal means is disposed insaid first position under normal operating conditions..Iaddend..Iadd.60. A scroll machine as claimed in claim 57 wherein theexistence of a vacuum at the suction inlet of said compressor will causesaid seal means to move from said first position to said secondposition. .Iaddend..Iadd.61. A scroll machine as claimed in claim 57wherein said pressurized fluid reacts against a surface of said onescroll member to bias said one scroll member toward the other scrollmember. .Iaddend..Iadd.62. A scroll machine as claimed in claim 57wherein said cavity is exposed to a surface of said non-orbiting scrollmember. .Iaddend..Iadd.63. A scroll machine as claimed in claim 62wherein said working fluid under pressure reacts against said surface tobias said non-orbiting scroll member toward said orbiting scroll member..Iaddend..Iadd.64. A scroll machine of claim 57 wherein said seal meansfloats axially in response to the ratio between said suction pressureand said discharge pressure. .Iaddend..Iadd.65. A scroll compressorcomprising:(a) a hermetic shell; (b) an orbiting scroll member disposedin said shell and having a first spiral wrap on one face thereof; (c) anon-orbiting scroll member disposed in said shell and having a secondspiral wrap on one face thereof, said spiral wraps being intermeshedwith one another; (d) means for causing said orbiting scroll member toorbit about an axis with respect to said non-orbiting scroll memberwhereby said wraps will create pockets of progressively changing volumeto compress a working fluid between a suction pressure zone defining asuction pressure and a discharge pressure zone defining a dischargepressure zone; (e) means defining a cavity disposed within one of saidscroll members; (f) means defining a leakage path between said dischargepressure zone and said suction pressure zone; (g) means for supplyingsaid working fluid to said cavity at a pressure intermediate saidsuction pressure and said discharge pressure; and (h) movable seal meansdisposed in said cavity for closing said leakage path by engaginganother component of said compressor, said seal means being disposedunder normal operating conditions of said compressor in a first positionwherein said seal means isolates said discharge pressure zone from saidsuction pressure zone and wherein said seal means moves within saidcavity to a second position wherein said fluid in said dischargepressure zone is leaked into said suction pressure zone when the ratioof said discharge pressure to said suction pressure exceeds a predefinedlimit. .Iaddend..Iadd.66. A scroll machine as claimed in claim 65wherein said working fluid being supplied to said cavity reacts againstsaid scroll members to bias said scroll members together. .Iaddend.